Drug therapy complications are common in the ambulatory setting and often lead to hospitalization. Between 5 and 10 percent of all hospital admissions in the United States have been attributed to a drug therapy complication. Among the elderly, this figure has been reported to be between 10 and 30 percent. In one report, the overall direct cost of admissions to hospitals or long-term care facilities due to noncompliance were estimated to be approximately $30 billion a year, the indirect cost estimate exceeded $50 billion annually (Task Force for Compliance 1993). A six-month study of adverse drug events at Brigham and Women's Hospital and Massachusetts General Hospital in Boston disclosed that errors occurred at every point in the medication use process, from the initial order (49 percent of errors) through transcription (11 percent), dispensing (14 percent), and administration of medication (26 percent). When one considers that approximately 3.75 billion drug administrations (Manasse 1989) are made annually to patients in U.S. hospitals, with 20 steps per administration, the opportunities for things to go wrong are considerable.
Leape et al. (1995) examined the data from the Brigham and Women's Hospital and the Massachusetts General Hospital study and identified 16 major system failures that could lead to treatment errors and drug therapy complications. Many of these failures were attributed to one or both of two basic problems:                Failures in communication, particularly in the transfer of drug and/or patient information from one health care provider to another, leading to incorrect therapeutic decisions based on incomplete information; and        Inadequate information, leading to errors in drug choice, dosage, timing, and administration.        
The US Food and Drug Administration (FDA) in collaboration with the Center for Education and Research on Therapeutics have developed a module termed Preventable Adverse Drug Reactions: A Focus on Drug Interactions (http://www.fda.gov/cder/drug/drugReactions/default.htm), which is incorporated herein by reference. This report regarding hospitalized patient populations estimates that 6.7% of hospitalized patients have a serious adverse drug reaction, with a fatality rate of 0.32%. If this estimate is correct, then there are more than 2 million serious adverse drug reactions (ADRs) in hospitalized patients, causing over 100,000 deaths annually. If true, then ADRs are the 4th leading cause of death—ahead of pulmonary disease, diabetes, AIDS, pneumonia, accidents, and automobile deaths.
These statistics do not include the number of ADRs that occur in ambulatory settings. Also, it is estimated that over 350,000 ADRs occur in U.S. nursing homes each year. Approximately two thirds of all patient visits to physicians result in prescriptions, and the rate of ADRs increases substantially after a patient is taking four or more medications. The exact number of ADRs is not certain and is limited by methodological considerations. However, whatever the true number is, ADRs represent a significant public health problem that is, for the most part, preventable.
Recent publications have shown that many adverse drug reactions can be prevented and detected through the use of systems interventions. For example, many health systems have instituted new technologies to minimize patient injury due to medication errors and drug-drug interactions. Tools like computerized physician order and prescription entry and bar coding systems have demonstrated tangible benefits. The potential for reducing medication errors by using computerized medical records as well as drug-interaction screening software that detects and alerts the physician and/or pharmacist to potentially serious drug interactions has been recognized.
The following references are related to this discussion, and are incorporated herein by reference:
Committee on Quality of Health Care in America: Institute of Medicine. To err is human: building a safer health system. Washington, D.C.: National Academy Press; 2000.
Lazarou J et al. Incidence of adverse drug reactions in hospitalized patients: A meta-analysis of prospective studies. JAMA 1998; 279:1200-1205.
Gurwitz J H et al. Incidence and preventability of adverse drug events in nursing homes. Am J Med 2000; 109(2):87-94.
Johnson J A et al. Drug-related morbidity and mortality. A cost-of-illness model. Arch Intern Med 1995; 155(18):1949-1956.
Leape L L et al. The nature of adverse events in hospitalized patients. Results of the Harvard Medical Practice Study II. N Engl J Med 1991; 324(6):377-384.
Classen D C et al. Adverse drug events in hospitalized patients. Excess length of stay, extra costs, and attributable mortality. JAMA 1997; 277(4):301-306.
Schappert S M. Ambulatory care visits to physician offices, hospital outpatient departments, and emergency departments: United States, 1997. National Center for Health Statistics. Vital Health Stat. 1999; 13(143).
National Association of Chain Drug Stores. 2000 community pharmacy results. 2001. Alexandria, Va.
Jacubeit T et al. Risk factors as reflected by an intensive drug monitoring system. Agents Actions 1990; 29:117-125.
Leape L L et al. Systems analysis of adverse drug events. ADE Prevention Study Group. JAMA 1995; 274(1):35-43.
Raschetti R et al. Suspected adverse drug events requiring emergency department visits or hospital admissions. Eur J Clin Pharmacol 1999; 54(12):959-963.
Bates D W et al. Effect of computerized physician order entry and a team intervention on prevention of serious medication errors. JAMA 1998; 280(15):1311-1316.
Evans R S, Pestotnik S L, Classen D C, Horn S D, Bass S B, Burke J P. Preventing adverse drug events in hospitalized patients. Ann Pharmacother 1994; 28(4):523-527.
Gebhart F. VA facility slashes drug errors via bar-coding. Drug Topics 1999; 1:44.
Committee on Quality of Health Care in America: Institute of Medicine. To err is human: building a safer health system. Washington, D.C.: National Academy Press, 2000.
Cavuto N J, Woosley R L, Sale M. Pharmacies and prevention of potentially fatal drug interactions. JAMA 1996; 275: 1086-1087.
Smalley W, Shatin D, Wysowski D K, Gurwitz J Andrade S E, Goodman M, et al. Contraindicated use of cisapride: impact of food and drug administration regulatory action. JAMA 2000; 284(23):3036-3039.
Manasse H R Jr. Medication use in an imperfect world: drug misadventuring as an issue of public policy, Part 1. Am J Hosp Pharm. 1989 May; 46(5):929-44.
Manasse H R Jr. Medication use in an imperfect world: drug misadventuring as an issue of public policy, Part 2. Am J Hosp Pharm. 1989 May; 46(5):1141-52.